or melon, are
conceived to form one thing; and that on account of their close
relation, which makes them affect the thought in the same manner, as if
perfectly uncompounded. But the mind rests not here. Whenever it views
the object in another light, it finds that all these qualities are
different, and distinguishable, and separable from each other; which
view of things being destructive of its primary and more natural
notions, obliges the imagination to feign an unknown something, or
original substance and matter, as a principle of union or cohesion among
these qualities, and as what may give the compound object a title to be
called one thing, notwithstanding its diversity and composition.

The peripatetic philosophy asserts the original matter to be perfectly
homogeneous in all bodies, and considers fire, water, earth, and air, as
of the very same substance; on account of their gradual revolutions and
changes into each other. At the same time it assigns to each of these
species of objects a distinct substantial form, which it supposes to be
the source of all those different qualities they possess, and to be a
new foundation of simplicity and identity to each particular species.
All depends on our manner of viewing the objects. When we look along the
insensible changes of bodies, we suppose all of them to be of the same
substance or essence. When we consider their sensible differences, we
attribute to each of them a substantial and essential difference. And
in order to indulge ourselves in both these ways of considering our
objects, we suppose all bodies to have at once a substance and a
substantial form.

The notion of accidents is an unavoidable consequence of this method
of thinking with regard to substances and substantial forms; nor can
we forbear looking upon colours, sounds, tastes, figures, and other
properties of bodies, as existences, which cannot subsist apart, but
require a subject of inhesion to sustain and support them. For having
never discovered any of these sensible qualities, where, for the reasons
above-mentioned, we did not likewise fancy a substance to exist; the
same habit, which makes us infer a connexion betwixt cause and effect,
makes us here infer a dependence of every quality on the unknown
substance. The custom of imagining a dependence has the same effect as
the custom of observing it would have. This conceit, however, is no more
reasonable than any of the foregoing. Every quality being a d